In prior art gate operator mechanisms, the linkage between the prime energy source, such as an electric motor, and the gate may be non-linear in nature. If the high torque end of the torque characteristic is used, for example, for initiating the opening portion of the cycle, it is not available for the initiation of the closing portion of a complete cycle. Since a much higher starting torque is required to start the relatively large mass of the gate into motion than is required to sustain the motion, the prime energy source must be sized to accommodate the larger starting torque requirement. Motors in the range of nearly a full horsepower may be required to fill the starting torque requirements under these conditions. These motors are relatively expensive and bulky. A typical prior art system which displays these characteristics is the Model AHSG Heavy Duty Swing Gate Opener, manufactured and available from the Stanley Works, 5740 East Nevada Avenue, Detroit, Mich. 48234. This unit utilizes either a 1/2 or 1 horsepower electric motor as a prime mover, depending upon the size of the swinging gate. There are other models which range down to 1/3 horsepower. All of these prior art systems are designed for mounting on the opening direction side of the swinging gate.
Because of the high currents required to run the large motor required for the prior art mechanism, it has not been feasible to provide battery standby power for those cases where the electrical energy source fails. This has meant that those gates are inoperable during such a power failure; a situation that can be inconvenient, at best, and dangerous in some emergency situations where access to the gated drive may be blocked for an uncertain length of time. Conversely, in prior art gate operator mechanisms, non-linear linkages have provided high torque for initiating both the opening and closing portions of a complete cycle. However, such mechanisms have required that the operator assembly be located next to the side of the gate post toward which the gate is to open. This means that the gate operator must be located outside the secure area when it is desired that the gate open outward. Such prior art operators suffer an additional limitation in that once located, gate rotation can not be changed. That is, a gate which opens outward from the secure area can not be adapted to open into or toward the secure area, and vice versa.